Impulse phase measuring system



Nov. 10, 1942. L. E. NORTON IMPULSE PHASE MEASURING SYSTEM Filed Oct. 31, 1941 -w- TIME Patented Nov. 10, 1942 IMPULSE PHASE MEASURING SYSTEM Lowell E. Norton, Collingswood, N. J assignor to Radio Corporation of America, a corporation of Delaware Application October 31, 1941, Serial No.417,381

. 8 Claims.

This invention relates to an impulse phase measuring system, and more particularly-to a system employing negative transconductance tubes for measuring the phase of an impulse potential with respect to a reference potential of the same frequency; the principal object of my invention being to provide a novel circuit by means of which the phase of an impulse potential may be compared with that of a reference potential. o

In accordance with this'invention l employ a pair of pentodes in which the anodes are connected in parallel relation and the suppressor grids are connected in parallel relation, the screen grids being connected to provide a pushpull, balanced output circuit. A reference sinusoidal potential is applied to the inner grid electrodes of the tubes in push-pull relation, and the impulse potential is applied to the suppressor grids. The output circuit of the screen grids includes a pair of serially connected resistors across which is connected a suitable meter. The system is so arranged that, when a negative impulse potential is applied to the suppressor grids in parallel which exceeds a negative biasing potential applied to the suppressor grids, one or the other of the tubes will provide a negative transconductance between the suppressor and screen grids to produce a relatively greater current in one or the other of the aforementioned serially connected resistors, whereby to effect a deflection of the meter indicativeof the phaserelation between the impulsepotential and the reference potential. I

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, aswell as-additional ob-' jects and advantages thereof, will best be understood from the following description of one embodimentthereof, when read in connection with the accompanying drawing in which Figure 1 is a circuit diagram of one form of my invention, and

Figure 2 shows a set ofcurves of the voltages to be compared.

Referring more particularly to the drawing, I have shown a pair of pentode vacuum tubes T1 and T2, the .former being provided with a cathode l, a grid 3-, a screen grid 5, a suppressor grad I, and an anode 9, and the latter having a cat ode l I, a grid l3, a screen grid IS, a suppressor grid l1, and an anode IS. The suppressor grids I and I1 are connected in parallel relation, and

the anodes 9 and iii are also connected to each other in parallel relation. The screen grids are connected to each other through a pair of serially connected resistors 2| and 23 across which is connected a suitable indicating device, such as a voltage meter 25. The junction 21 of the resistors 2| and 23 is connected through a battery 29 to the cathodes l and l I, the cathode to screen grid circuits thus being connected in push-pull relation and the battery 29 applying a positive potential to the screen grids 5 and I5 relative to the cathodes l and II, respectively. The battery 29 is also connected to the anodes 9 and I9 through a resistor 3| for applying a suitable potential to the anodes to produce the desired negative transconductance, and a capacitor 33 may be connected between the cathodes and the anodes for a purpose presently to be set forth.

The reference potential E1 is applied to the grids 3 through a transformer 35, a battery 31 which is connected between the cathodes and a midtap on the secondary winding of the transformer 35, and resistors 4| and 43, the battery 31 maintaining the grids 3 and I3 negative with respect to their respectively associated cathodes I and 3. It will be apparent, therefore, that the reference voltage E1 is fed to the grids 3 and I3 in push-pull relation. The impulse Potential E is applied to the suppressor grids l and I1 by-a suitable input circuit 45, a battery 81 serving to apply a predetermined negative biaspotential on the screen grids land I! through a resistor 49.

The operation of the measuring system consti- 35 tuting my present invention is as follows:

For the signal condition that the impulse voltage E equals zero, the initial biasing potentials of the batteries 31 and 41 and the value of the resistances 2| and 23 are such as to make the currents between the cathode l and the suppressor grid 1 on the one hand, and the cathode II and the suppressor grid 11 on the other hand, each approximately zero. The reference voltage E1 is preferably sinusoidal in which case larger deflections of the voltmeter 25 will result if the series resistances 4| and 43 are inserted, since the currents from the cathode l to .the screen grid 5 andthe cathode II to the-screen grid l5 will then be more nearly constant and a maximum during a greater portion of each half cycle of the reference potential E1, when the impulse potential E is applied. For smaller deflections of the voltmeter 25, the resistances 4| and I3 55 may be omitted. If the reference potential E1 is a sinusoidal wave with its top squared, as

each be zero and the current through the meter 25 will be zero. v

I The plates or anodes 9 and I9 serve merely as accelerating electrodes. When a negative 1mpulse potential E.which is narrow as compared with the reference potential E1, as shown in Figure 2, is applied to the suppressor grids I and I1, then, for the condition when the grid 3 happens to be positive with respect to its cathode I and the grid I3 is negative with respect to its cathode II, electrons which'would have passed from the cathode I through the grids 3, 5 and I and on to the anode 9 are turned back by the negative potential on the suppressor grid I and appear *on the screen grid 5. Current therefore flows through the circuit in which the resistor 2| appears. During the same time, since the reference potentials on the grid 3 and the grid I3 are 180 degrees out of phase, the inner grid I3 goes more negative .and few or no electrons pass from the cathode II through the grid I3 to the electrodes I5, I! and I9. Current through the circuit in which the resistor 23 appears therefore remains approximately zero. Hence, the meter 25 will deflect either to the right or to the left depending upon the meter polarity If the phase of the potentials E and E1 is changed so that the impulse occurs when the grid are possible. I, therefore, desire that my invention shall not be limited except insofar as is made necessary by the prior art and by the spirit of the appended claims.

I3 is positive and the grid 3 is negative, instead of the reverse condition, current will flow through the circuit of resistor 23 and the current through the circuit of the resistor 2| will remain approximately zero. The deflection of the meter 25 will, therefore, be opposite in direction to that of the first case considered above.

The only condition for which the cathode I to grid 3 potential and the cathode II to grid I3 potential will be equal occurs when the impulse potential E appears when the reference potential E1 is at zero, or at the points A in Figure 2. For this condition, the currents through the circuit of the resistor 2| and that in the circuit of the resistor 23 are equal and approximately zero, so that the deflection of the meter 25 will be zero.

As has been explained heretofore, a zero defiection of the meter 25 indicates that the impulsive potential occurs at the zero magnitude of the reference potential E1. A deflection of the meter in one direction indicates a phase difierence either positive or negative (depending upon meter polarity) from a zero condition, while a meter deflection in the other direction indicates a phase 'difference of the opposite sign. Furthermore, the meter deflection is a function of the phase deviation from zero condition so that, by calibration, the meter 25 will indicate directly the phase relation between the impulse potential E and the reference potential E1. For most tubes T1 and T2, it is desirable to provide the capacitor 33 between the accelerating electrodes or anodes 9 and I 9 and their respective cathodes I and II in order to obtain maximum value 'of negative transconductance during the period of impulse,

Although I have shown and described but one embodiment of my invention, it will be apparent to those skilled in the art that many other modifications, as well as variations in that described,

I claim as my invention; a

1. In a system for indicating the phase relation between an impulse potential and a sinus oidal reference potential, the combination of a pair of vacuum tubes each having a cathode, a first grid, a second grid, a third grid and an anode in the order named, said anodes being connected in parallel relation and said third grids being also connected in parallel relation, means con- .necting said second grids in balanced relation to provide a balanced output circuit, an indicating device connected to said output circuit, means for feeding said reference potential to said first grids, and means for feeding said impulse potential to said third grids.

2. In a system for indicating the phase relation between an impulse potential and a sinusoidal reference potential, the combination of a pair of vacuum tubes eachhaving a cathode, a first grid,

a second grid, a third grid and an anode in the order named, said anodes being connected in parallel relation and said third grids being also connected in parallel relation, means-connecting said second grids in push-pull relation to provide a'balanced output circuit, an indicating device connected to said output circuit, means for'feeding said reference voltage in push-pull relation to said first grids, and means for feeding said impulse potential to said third grids. I

3. In a system forindicating the phase relation between an impulse potential and a sinusoidal reference potential, the combination of'a pair of vacuum tubes each having a cathode, a first grid, a second grid, a third grid and an anode in the order named, said anodes being connected in parallel relation and said third grids being also connected in parallel relation, means for applying a negative bias potential to said third grids relative to said cathodes, means connecting said second grids in balanced relation to proi' ide a balanced output circuit, an indicating device con- \nected to said output circuit,means for feeding said reference potential to said first grids, and means for feeding said impulse potential to said third grids, the application of a negative potential to said third grids by said impulse potential in excess of said negative bias potential causing an increase of current in said output circuit and producing an indication on said indicating device representing the phase relation between said potentials.

4. In a system for indicating the phase relation between an impulse potential and a sinusoidal reference potential, the combination of a pair of vacuum tubes each having a cathode, a first grid, a second grid, a third grid and an anode in the order named, said anodes being connected in parallel relation and said third grids being also connected in parallel relation, means for applying a negative bias potential to said third grids relative to said cathodes, means connecting said second grids in balanced relation to provide a balanced output circuit, an nected to said output circuit, means for feeding said reference potential 'to said first grids, said last-named means including means for applying a negative bias to said first grids, and means for feeding said impulse potential to said third grids, the application of a negative potential to said third grids by said impulse potential in exindicating device concess of said first-named negative bias potential a acterized in that the means connecting said second grids includes a pair of series connected resistors, and characterized further in that said indicating device is connected across said resisters.

6. The invention set forth in claim 4 characterized in that the means connecting said second grids includes a pair of series connected resistors, characterized further in that said output circuit includes av connection between the Junetion ofsaid resistors and each f said cathodes whereby the circuits of said second grids are connected in push-pull relation, and characterized still further in that said indicating device is connected across said resistors.

7. The invention set forth in claim 4 characterized by the addition of means for applying to said second grids a. bias potential which is positive relative to said cathodes.

8. The invention set forth in claim 4 characterized by the addition of means including a resistor for applying to said anodes a predetermined positive biasing potential relative to said cathodes, and characterized further by the addition of a capacitor connected between said cathodes and said anodes.

LOWELL E. noR'roN. 

